In the prior art of writing and its display, in which a hand-held writing instrument and a writing display surface are used, two different modes are employed, either application of material or application of energy. For the application of a writing material upon the material of a writing display surface, common writing materials are graphite, ink, wax, and chalk. Common hand-held instruments are pens, pencils, crayons, and chalk sticks. Common materials for the writing display surface are paper, glass, and slate.
For writing by the application of energy, a hand-held instrument is used for supplying energy for interacting with material associated with a surface of reference luminosity thereby exhibiting a visual contrast between the luminosity of the writing and the luminosity of the reference surface.
This energy application mode of writing is further divided into two classes based upon the type of energy supplied by the hand-held instrument. In the first class of the energy application mode of writing, contact force of the hand-held instrument upon the writing display surface causes a translation of material which provides for an alteration in the luminosity of the reference surface. Common examples are writing on clay or wax tablets using pointed stylus as hand-held instrument.
In the second class of the energy application mode of writing, the energy supplied by the hand-held instrument to the surface of reference luminosity is by means other than physical contact force; that is, the energy supplied is field energy or wave energy. Prior art shows that electromagnetic wave energy of various wavelengths has been used for writing on display surfaces whose luminosity is altered by interaction with electromagnetic wave energy. Examples of such prior art devices are found in Christy U.S. Pat. No. 3,443,332 issued May 13, 1969 and Melchior U.S. Pat. No. 3,836,243 issued Sept. 17, 1974.
However, the prior art devices do not provide for selective, local erase of displayed writing on the display surface by direct application of a hand-held erasing instrument in close proximity to the writing.
In view of the above, it is an object of the present invention to provide a writing and display apparatus which includes a hand-held write/erase instrument having means for transferring energy for writing either magnetic field or electric field energy or electromagnetic wave energy, to a writing and display surface of reference luminosity thereby effecting writing which is retained for an appropriate length of time; and said hand-held write/erase instrument having further means for transferring energy of erasing to written-upon regions when placed in close proximity to such displayed regions thereby effecting a selective, local erasure of the writing and a return of the luminosity of the written-upon regions to that of the reference luminosity.
Yet another object of the invention is to provide a writing and display apparatus which includes hand-held write/erase instrument and which, for erasing, does not require removal of a writing material from the display surface, such as chalk from a blackboard with its attendant dust and cleaning problems.